Existing technologies to locate objects or boundaries in a complex medium (i.e., to determine locations of the objects or the boundaries in the medium), and to track the objects or the boundaries as they move, are limited in their ability to operate with sufficient safety, speed and/or accuracy for various applications, e.g., before, during and after movement and deformation of the medium.
Improved localisation and tracking of obj ects or boundaries in a medium may be desirable in one or more of the following example applications:                in mining (e.g., surface mining or sub-surface mining), it may be desirable to locate and/or track boundaries of ore bodies in rock, e.g., after the rock has been blasted and therefore disrupted;        in mining, it may be desirable to locate and/or track underground explosive devices, e.g., before and/or after a blast;        in mining or exploration, it may desirable to track drill bits in holes or wells in rock or ground;        in emergencies, it may be desirable to locate and/or track a person or a piece of equipment buried in an avalanche, a landslide, or a collapsed structure;        in civil engineering and construction, it may be desirable to locate and/or track a person or a piece of equipment inside a structure; and        in geological, seismological or construction monitoring, it may be desirable to monitor rock, earth, foundations or structures to determine movement over time.        
The lack of available or sufficient localisation and tracking in the above situations may be substantially detrimental. For example, in mining operations, if the boundary between ore and waste is not accurately localised, mixing of ore and waste (which may be referred to as “ore dilution”) following a blast may lead to measurable economic losses in a mining operation. These losses can arise from the unnecessary processing of rock whose ore content is below an economic limit, and from losses of value arising from not processing rock whose ore content is above an economic boundary and that is lost as waste material. For example, ore-dilution losses in a single typical gold mine may be up to about $1 million per year, depending on the price of gold, the mine geology, and the mining techniques, etc.
It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative.